The field of this invention is that of safety seat belt systems and the like and the invention relates more particularly to over-the-shoulder automotive safety belts having latch means providing tensionless comfort settings for the belts during use and having remotely operable thermostat metal means to release the latch means and permit automatic belt retraction after use.
Conventional automotive safety belt systems permit a length of belt to be withdrawn from a supply reel and passed over the shoulder of a vehicle operator or passenger to be buckled to a support connected to the vehicle floor. In early systems, springs automatically retracted the belt after use and, by applying a retracting spring force to a buckled belt, also serve to draw the belt snugly against the operator's shoulder to assure that only a safe length of the belt was left in the withdrawn position. The length of belt would then be locked in its withdrawn position by an inertially operated lock during any abrupt stopping of the vehicle to provide restraint to protect the operator from injury.
More recently, such over-the-shoulder systems have included comfort means which permit the operator to pull out a small additional length of belt and to latch that additional belt in withdrawn position to release the tension on the belt so that, while the length of belt still provides safe restraint to protect the operator, it rests more comfortably on the operator's shoulder during normal vehicle operation. However, such tensionless systems have typically required the user to reset the system after use. In one known system, for example, where a stylus pawl is adapted to engage a ratchet for providing the tensionless belt setting, the seat belt user is required to pull on the belt in a particular manner to release the pawl engagement with the ratchet after unfastening the belt and before leaving the vehicle so that the withdrawn length of the belt will be retracted onto the belt supply reel. If that user action is omitted, the length of belt remains withdrawn and clutters the passenger space during reentry of the vehicle until the user resets the retraction system.
Other tensionless systems have provided latch release means to permit the belt to be automatically retracted after use but such automatic release systems have been expensive and cumbersome. In one widely used system for example, a ratchet and pawl latch is arranged to be actuated by a plunger which is set or released by closing or opening of the vehicle door. In that arrangement, closing of the door positions the plunger so that, when the vehicle operator buckles his belt and then pulls out a small additional length of belt to provide a desired tensionless or comfort setting, the ratchet and pawl latch holds the additional length of belt in its withdrawn position. When the operator subsequently unbuckles the belt and opens the vehicle door, the plunger moves and releases the latch and permits the belt to be automatically retracted. In that system, it has been difficult and expensive to mount the plunger to achieve reliable system operation. Usually the mounting location for the system has been limited by the need for mechanical linkage between the system and the door-mounted plunger. More importantly, the spring requirements of the plunger have been such that they have added very undesirably to the forces required for closing the vehicle door.
A seat belt system having a new clutch type of comfort latch has now been proposed and it has been suggested that a strip of thermostat metal be arranged to serve as a latch release in that system. As proposed, the thermostat metal strip would be electrically heated by the same electrical circuit which energizes the interior dome light of the vehicle to release the latch when the vehicle door is opened. In that way, the latch release could be operated at a location remote from the door and no excessive door closing forces would be imposed. In the proposed new system however, the comfort latch extended radially from one end of a belt reel shaft and the proposed thermostat metal strip was mounted at one end to extend tangentially relative to the shaft axis to intercept the rotating latch on the distal end of the strip, the strip being adapted to flex when heated to move its distal end in a radial direction relative to the shaft to release the latch. As thus proposed, the latch release system would be expensive and unreliable. That is, the thermostat metal strip would tend to bow when heated rather than to release the latch. A comfort latched seat belt system having such a release arrangement would also tend to require excessive operating and resetting times, would be subject to inadvertent tripping due to changes in ambient temperature, would be unreliable in latch release operation, and would tend to be subject to overheating if vehicle doors were left opened for an extended period of time.